Amorphous calcium sodium pyrophosphate

ABSTRACT

This invention relates to novel partially dehydrated amorphous calcium sodium pyrophosphate and to the production of such compounds. Also this invention relates to the process for the use of these compounds to gel aqueous solutions of some polyols and to the gels obtained therefrom.

0 United States Patent 11 1 1111 3,875,289

Kim 5] Apr. 1, 1975 AMORPHOUS CALCIUM SODIUM 2.601.395 6/1952 Hatch 23/105 PYROPHOSPHATE 3,244,478 7/1961 Stah1heber...'... 3.409.393 11/1968 Stahlheber 23/108 [75] Inventor: Keun Young Kim, Chesterfield, Mo. [73] Assignee: Monsanto Co., St. Louis, Mo. P g g VBTRZ H u Assistant .\'aminer regory e er [22] Flled: 1971 Attorney, Agent, or Firm-11. C. Stanley; Roy J. 211 App] 110, 05 Klostermann; J. E. Maurer 52 Us. 01 423/306, 423/305, 423/311 [571 ABSTRACT 51 Int. (:1. C0lb 15/16, c0115 25/26 This Invention relates to novel Partially dehydrated [58] Field of Search 23/105, 106, 106 A, 107, amorphous calcium Sodium py p p and to the 23 03 [09 production of such compounds. Also this invention relates to the process for the use of these compounds to 5 References Cited gel aqueous solutions of some polyols and to the gels UNITED STATES PATENTS Obamed therefrom 2,539.305 1 1951 Hatch 23/105 x 2 Claims, N0 Drawings AMORPHOUS CALCIUM SODIUM PYROPHOSPHATE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel partially dehydrated amorphous calcium sodium pyrophosphates and to processes for preparing such compounds and to the use of these compounds to gel aqueous solutions of polyols and the resulting gels.

2. Description of the Prior Art Gels which are two-phase colloidal systems consisting of a solid and a liquid have many uses. for example, in the food areas such as dessert puddings. the pharmaceutical areas such as a medicated cream. or in rub-on sticks. Most hydrocolloids used are expensive. Some of the raw material used in preparing these gels are not available in large supplies. Some polyols. sorbitol for example. are available in large quantities at low costs. Consequently. a process for producing polyol gels would be an advancement in the art.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to polyol gels and to a process for preparing polyol gels by utilizing a novel compound. i.e.. a partially dehydrated amorphous calcium sodium pyrophosphate, as a gelling agent. Another aspect of this invention is a process for preparing the novel compounds. The processes of this invention provide polyol gels which may be utilized for cosmetic and pharmaceutical purposes. The invention will be better understood from the following detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION The novel compounds of this invention are partially dehydrated amorphous calcium sodium pyrophosphates represented by the formula CaNa- P- O zvH O wherein .r has a value of from about 0.1 to about 2.0. This compound is used to gel aqueous solutions of some polyols as will hereinafter be set forth.

These compounds may be prepared by dehydrating calcium sodium pyrophosphate tetrahydrate. The tetrahydrate is heated at a temperature of 60C to about 400C. preferably from about 200C to about 300C. The tetrahydrate is heated until the desired amount of water of hydration is removed. The calcium sodium pyrophosphate tetrahydrate can be prepared by neutralizing a lime slurry with sodium acid pyrophosphate or by reacting a calcium salt with pyrophosphate in aqueous alkaline medium.

In most instances. at least 0.5 weight percent of partially dehydrated amorphous calcium sodium pyrophosphate must be used to gel the aqueous solutions of polyols. An amount lower than that of 0.05 weight percent usually results in unsatisfactory gelling.

There is no upper limit on the amount that may be used. For example. hard gels are obtained with 40 weight percent and even with 90 weight percent. A satisfactory operating range is from 0.1 to about 10 weight percent with 0.5 to about 5 weight percent being preferred.

As mentioned before,aqueous solution of polyols may be gelled with the novel compounds of this invention. These polyols include sorbitol. mannitol, and glycerine. Sorbitol is preferred. Such aqueous solutions of polyols contained about at least weight percent of the polyols based on the total weight of the aqueous solution of polyols. Generally in amounts below 10 weight percent the aqueous solution of polyols is gelled to very weak structure. There is no upper limit on the amount of polyols that may be present. for example. gelling is obtained with up to the saturation point of aqueous solution of polyols. It is preferred to use aqueous solutions of polyols containing about 30 weight percent to about weight percent based on the total weight of the aqueous solution of polyols as good gels are formed.

The aqueous solution of polyol may be gelled in any convenient vessel. The calcium sodium pyrophosphate is added to the aqueous solution of polyols. It is preferred to add the calcium sodium pyrophosphate to the aqueous solution of a polyol with intense agitation. The mixture is transferred to the desired container to gel. Various molds can be used to produce varying shapes.

The temperature at which the reaction is conducted in accordance with this invention can be conventional. For example. it can range from the freezing point of the reaction mixture to about 100C. but the preferred operating temperature is from about 1 0C to about C with temperature of about room temperature to about 60C being especially preferred.

The time required for a satisfactory degree of gelling in the process according to this invention depends upon a number of factors including temperature. concentration of polyols. degree of agitation during dispersion. presence of other ingredients. and amount of gellant utilized. In most instances. the aqueous solutions will take from about 10 minutes to 5 hours to gel the aqueous solutions of polyols.

However. when a soluble ortho or pyrophosphate is added in an amount of from about 800 ppm to 1.500 ppm, the gelling time is significantly reduced. If over 1,500 ppm is added the solution aggregates. If less than 800 ppm there is no appreciable reduction in gelling time. It is preferred to add about 1.000 ppm of sodium acid ortho or pyrophosphate.

The pH of the mixture of polyol solution of gellant for a satisfactory production of a gel is from about 5 to about 10, preferably 6.5 to 8.5.

The gels obtained according to this invention contain at least 10 weight percent of the polyols. and preferably 30 to about 70 weight percent, at least 0.05 weight percent of calcium sodium pyrophosphate and preferably 0.5 to about 5 weight percent, with the balance being water. Generally. the gel has a gel strength from about 500 dyne/cm to about 100,000 dyne/cm with 1,000 dyne/cm to about 40,000 dyne/cm being preferred. Gel strength is determined by using a I-Iaake Viscometer (Rotvisco) at the solwest speed, i.e., 0.03 rpm. Additionally, the gels are stable at a temperature up to about C.

The gels obtained in accordance with this invention have a wide variety of uses. for example, a sorbitol gel can be cast into a stick and used as a deodorant in same manner as those which are commercially available.

Numerous gels differing in texture. rheological properties, can be formed by incorporating other cosmetic. pharmaceutical ingredients and other hydrocolloids such as starch, agar, align. carrageenan, gum arbic, guar gum, pectin, gum tragaranth,, sodium carboxymethylcellulose and starch derivatives.

3 This invention is specifically illustrated by the following examples in which all parts, percentages or proportions are by weight unless otherwise indicated.

EXAMPLE l A weight percent aqueous solution of calcium chloride is added to a 15 weight percent aqueous solution of tetrasodium pyrophosphate in a suitable vessel until the pH reaches 7. The acicular crystals of calcium sodium pyrophosphate tetrahydrate are formed. The crystals are filtered. washed thoroughly, and dried at 60C. The calcium sodium pyrophosphate tetrahydrate is then heated at a temperature within the range of 175 to 200C for a period of 60 minutes until 3.2 moles of water of hydration is removed. The dehydrated solids were then ground. The structure of the material is now amorphous as determined by X-ray diffraction.

The above procedure was followed and a calcium sodium pyrophosphate having 0.8 moles of water of hydration. was obtained.

EXAMPLE II EXAMPLE III The procedure set forth in Example I was repeated with the exception that 2.5 moles of hydration water was removed.

To a 100 cc of an aqueous solution containing 45 weight percent sorbitol was added to 2 grams of the calcium sodium pyrophosphate having 2.5 moles of water. The solution was agitated and then set to a gel. The gel strength by a Haake Viscometer (Rotvisco) was 9,000 dyne/cm after 24 hours.

EXAMPLE IV To a 100 cc of an aqueous solution containing 45 weight percent sorbitol, 2 grams of ground calcium sodium pyrophosphate tetrahydrate is mixed. The same procedure is repeated with calcium sodium pyrophosphate having less than 0.1 mole of water of hydration. .ln,both cases no gelling is observed.

EXAMPLE V The procedure of Example 11 is repeated except that sodium acid pyrophosphate (Na H P O is added to the solution of polyol in an amount of 0.1 weight percent. The gelling rate is increased.

The above procedure was followed. In another run, monosodium orthophosphate (NaH PO is substituted for sodium acid pyrophosphate. For comparison purposes, a run was made without the addition of either sodium acid pyrophosphate or disodium orthophosphate. The results are given in the following table.

Two grams of the material prepared in Example I is added to cc of an aqueous solution of glycerine containing 45 weight percent of glycerine at a temperature of 25C. the glycerine mixture set up to a soft gel.

EXAMPLE VII The procedure set forth in Example VI is repeated with the exception that mannitol is substituted for glycerine.

EXAMPLE Vlll To a 100 cc of an aqueous sorbitol solution containing 45 weight percent of sorbitol are added 2 grams of the calcium sodium pyrophosphate prepared in Example I and 10 grams of titanium oxide. The mixture gels in about 5 hours to form a soft gel of cream consistency.

EXAMPLE [X To a 200 cc of an aqueous sorbitol containing 45 weight percent of sorbitol by weight are added 4 grams of the calcium sodium pyrophosphate prepared in Example 0.3 g methyl parahydroxybenzoate (i.e., methyl PARASEPT by Heyden) and 0.5 g perfume. The mixture was stirred vigorously for two minutes. The preparation was poured into a rubber stoppered glass tubing having approximately five-eighths inch inside diameter. It was allowed to gel in a rack that kept the tubing in a vertical position. After two or three hours, the cast stick was forced from the tubing by means of a plunger. The casting was cut to proper size to prepare deodorant sticks.

What is claimed is:

1. A partially dehydrated amorphous calcium sodium pyrophosphate represented by the formula CaNa P- O -xH O wherein .t' has a value of about 0.1 to about 2.0.

2. A process for preparing partially dehydrated amorphous calcium sodium pyrophosphate which comprises heating at a temperature within the range of about C to about 400C calcium sodium pyrophosphate represented by the formula CaNa P O '4I-I O until substantially 2 to about 3.9 moles of water of hydration are UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. Dated April 975 Inventor(s) n Young Kim It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 52 "0 5 weight pegcent" should be co rected to ead 0.05 weight percent a e-651m, 111;; "65 ei i n' ga o' d e corrected to read 'l algin" same column, line &5 "two or three" ehould be corrected to read "two to three" Eugncd and Sealed this A nest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN ('mnnzixsimzvr of Parents and Trudcmurkx 

1. A PROCESS FOR PREPARING PARTIALLY DEHYDRATED AMORPHOUS CALCIUM SODIUM PYROPHOS TEMPERATURE WITHIN THE RANGE OF ABOUT 175*C TO ABOUT 400*C CALCIUM SODIUM PYROPHOSPHATE REPRESENTED BY THE FORMULA CANA2P207.4H20 UNTIL SUBSTANTIALLY 2 TO ABOUT 3.9 MOLES OF WATER OF HYDRATION ARE REMOVED.
 1. A partially dehydrated amorphous calcium sodium pyrophosphate represented by the formula CaNa2P2O7.xH2O wherein x has a value of about 0.1 to about 2.0. 